Although type 2 diabetes is a major health problem in the older population, little is known about alterations in beta cell function specifically in older adults. The objective of this study in to investigate the role of postprandial hyperglycemia in insulin secretory dysfunction in older adults with postchallenge hyperglycemia. Chronic postprandial hyperglycemia in older adults may lead to insulin secretory dysfunction through the mechanism of glucose toxicity. Normalization of postprandial hyperglycemia with a therapeutic agent may lead to a decline in glucose toxicity and an improvement in insulin secretion. Acarbose, an alpha-glucosidase inhibitor, decreases carbohydrate absorption and improves postprandial hyperglycemia without having direct effects on insulin secretion or sensitivity. Older adults with postchallenge hyperglycemia will be assigned to treatment with acarbose or placebo in a randomized, double-blind manner. If eligible to participate, subjects will undergo baseline tests including: an intravenous glucose tolerance test (IVGTT) to assess insulin sensitivity and a glucose ramp clamp to assess insulin secretion. Subjects will take either acarbose or placebo for six weeks. At the end of the treatment period, subjects will have a second IVGTT and ramp clamp. Oral glucose tolerance testing and 72-hour continuous glucose monitoring will be performed at baseline and at completion of the dosing period to assess the degree of normalization of postprandial hyperglycemia.